Optical sensor for determining the concentrations of dyes and/or particles in liquid or gaseous media and method for operating the same

ABSTRACT

The invention relates to an optical sensor ( 1 ) for determining particle and/or dye concentrations in liquid or gaseous media and to a method for operating the same. The optical sensor ( 1 ) comprises at least one measuring head. The measuring head consists of an emitter unit ( 2 ) with a semiconductor emitting element ( 9 ), which emits visible emission light beams ( 8 ), and with a receiver unit ( 3 ) with a semiconductor receiving element ( 10 ). The portion of the emission light beams ( 8 ), which pass through an absorption section containing liquid or gaseous medium, is guided onto the receiving element ( 10 ). An evaluating unit ( 6 ) is coupled to the measuring head via electric leads ( 4, 4 ′), and the received signals, which are present at the output of the semiconductor receiving element ( 10 ), are evaluated inside said evaluating unit in order to determine the particle or die concentration.

The invention relates to an optical sensor for determining theconcentrations of dyes and/or particles in liquid or gaseous media, aswell as to a method for operating the same.

Determining such dye concentrations or particle concentrations ingaseous or liquid media is a problem encountered in different branchesof the industry.

In particular, the determination of dye concentrations in liquid mediarepresents a critical element in the waste-water control and furthermoreprovides an essential parameter for the control and monitoring ofrinsing processes, especially when washing dyed and imprinted textiles.With washing operations of this type, the goal basically is to have theshortest possible washing operation and thus also keep the waterconsumption as low as possible. One approach for optimizing such washingoperations consists of controlling the rinsing processes during thewashing of textiles in dependence on the actual dye concentrations inthe rinsing water. In the process, a rinsing process is stopped if thedye concentration in the rinsing water reaches a specific limit value.As a result, unnecessarily long rinsing processes can be avoided, whichcauses a reduction in the water consumption and noticeably shortens theduration of the washing operation.

However, this approach requires a continuous control of the dyeconcentration in the rinsing water during the rinsing processes.

A known method for determining dye concentrations in liquid media is theECOD measuring technique. With this technique, an electro-chemicaldetermination of the chemical oxygen demand of the liquid medium isrealized and the resulting value is used as parameter for the dyeconcentration.

This technique has the disadvantage that the measuring intervals fordetermining the chemical oxygen demand are in the order of magnitude ofseveral minutes. Owing to this high reaction time during thedetermination of measured values, this method is only conditionallysuitable for controlling rinsing operations during the washing oftextiles.

Optical measuring devices such as spectrophotometers can generally alsobe used for determining dye concentrations, wherein the disadvantage ofthese measuring devices lies in the high equipment expenditure. Afurther disadvantage is that for determining the dye concentration inthe rinsing water, samples of the rinsing water must be supplied bymeans of pumps to flow-through cells in which the dye concentration isthen determined. Apart from the required high equipment expenditure, thetime required for pumping the rinsing water samples into theflow-through cells is a further disadvantage. As a result, only atime-delayed determination of the dye concentration in the rinsing wateris possible, thereby leading to an undesirably high response time forthe control of the rinsing operation.

It is the object of the present invention to provide a device and amethod which allow a quick and precise determination of the particle anddye concentrations in liquid or gaseous media while the necessaryequipment expenditure remains low.

This object is solved with the features disclosed in claims 1 and 23.Advantageous embodiments and useful modifications are described in thedependent claims.

The optical sensor according to the invention, which comprises at leastone measuring head, is used for determining particle and/or dyeconcentrations in liquid or gaseous media. The measuring head consistsof a transmitting unit with at least one semiconductor transmittingelement that emits visible light rays, as well as a receiving unit withat least one semiconductor receiving element onto which the transmittedlight rays that pass through an absorption section filled with liquid orgaseous medium are guided. The measuring head is connected viaelectrical supply lines to an evaluation unit for evaluating the signalsreceived at the output of the semiconductor receiving element in orderto determine the particle and/or dye concentration.

The optical sensor according to the invention has a simple modulardesign and can thus be produced cost-effectively. The structuraldimensions of the measuring head for the optical sensor are small, sothat the measuring head can be positioned easily at a measuring locationand is flexible for use. The optical sensor is furthermore distinguishedby a robust construction which requires almost no maintenance.

One primary advantage of the optical sensor is that its measuring headcan also be used in the manner of an immersion sensor module, whereinthe optically active sensor elements provided in the measuring head areembodied as semiconductor components. As a result, the measuring headhas a small structural size and can be positioned easily in the liquidor gaseous media, such that a defined absorption section that is filledwith the liquid or gaseous media to be used is positioned between thesemiconductor transmitting element and the semiconductor receivingelement.

The transmitting unit with the semiconductor transmitting element andthe receiving unit with the semiconductor receiving element areencapsulated, so as to be liquid-impermeable, to prevent damage to themeasuring head in particular during the immersion into the liquidmedium.

The particle and/or dye concentration in the liquid or gaseous medium isdetermined by means of an absorption measurement, wherein the length ofthe absorption section can be specified precisely by securing thetransmitting unit and the receiving unit in position on a holder.

With an optical sensor embodied in this way, the particle and/or dyeconcentration in the liquid or gaseous medium itself can be determinedcontinuously and nearly without delay.

As a result, the sensor signals generated by the optical sensor can beused in particular for a fast and precise control of rinsing processesin a rinsing basin in which dyed textiles are washed.

It is a particular advantage in this case that only the measuring headof the optical sensor is immersed into the liquid medium. The unit forevaluating the sensor signals is positioned outside of the rinsing basinand is connected by means of electrical supply lines to the measuringhead.

As a result of its modular design, the optical sensor can be expandedeasily by simply connecting several measuring heads to the evaluationunit. As a result, it is possible to determine in particular the dyeconcentration of liquid media in several basins simultaneously by meansof the optical sensor. Accordingly, the rinsing processes in severalrinsing basins can be controlled by means of the sensor signals from anoptical sensor.

As a result of the modular configuration of the optical sensor, themeasuring heads can also be mounted on cells, in particular flow-throughcells, thus making it possible to determine the dye concentration or, ifapplicable, the particle concentration of liquid or gaseous media insidesuch cells.

According to the invention, the particle and/or dye concentrations in aliquid or gaseous medium are determined on the basis of an absorptionmeasurement, wherein the evaluated sensor signals are the signalsreceived at the semiconductor receiving element, onto which thetransmitting rays passing through the absorption section are guided. Thedetermination of the dye concentration in the liquid or gaseous mediumis based on the Lambert-Beer Law.

According to the Lambert-Beer Law, the weakening of the transmittinglight rays passing through the absorption section filled with the liquidor gaseous medium is defined by an extinction value which is the productof the layer thickness for the absorption section and an extinctioncoefficient that depends on the wavelength of the transmitting lightrays, as well the dyes and/or particles contained in the liquid orgaseous medium.

Accordingly, the absorption measurement realized with an optical sensoris dependent on the sensor parameters, in particular the wavelength ofthe transmitted light rays.

Prior to realizing the measurements, a calibration operation istherefore carried out to eliminate the dependence of the absorptionmeasurement on sensor-specific parameters, wherein the optical sensor isused to rate the liquid or gaseous medium with predetermined, knownparticle or dye concentrations. From this, a sensor-specific extinctionvalue is determined as reference value for the values obtained duringthe subsequent measuring operations.

The measuring results are thus independent of the characteristics of theoptical sensor. It is particularly advantageous that optical sensorswhich do not emit monochromatic light can also be used when eliminatingthe dependence of the measuring results on the wavelength.

The only requirement for a precise determination of the particle and/orcolor concentration in the liquid or gaseous medium is that thewavelength range for the transmitting light rays is within the colorspectrum of the dye that must respectively be determined.

It has proven advantageous if semiconductor transmitting elements areused which emit visible light rays at the wavelength range of 400-700nm, wherein the spectral bandwidth for the transmitting light rayspreferably is less than 100 nm.

The use of semiconductor transmitting elements which emit light rays ata wavelength range of approximately 470 nm has proven particularlyadvantageous. With this embodiment of the optical sensor, a broadspectrum of different types of dyes can be detected since these absorblight in the aforementioned wavelength range.

One particularly advantageous use of the optical sensor according to theinvention is for determining the soot content and/or the metal abrasioncontent in engine oils of motor vehicles and the like. Furthermore, theoptical sensor according to the invention can be used for determiningparticle concentrations in exhaust air and thus in the area of emissionprotection. Finally, the optical sensor can also be used for determiningpollutants in waste water.

The optical sensor according to the invention can furthermore be usedfor determining pollutants in the exhaust gases of motor vehicles.

In addition, the optical sensor according to the invention can be usedfor the quality control in industrial processes, for example forcontrolling the pigment or particle concentrations in varnishes as wellas the dye concentrations in dye baths used for dying textiles.

The invention is explained in the following with the aid of the drawingwhich shows in:

FIG. 1 A schematic representation of an exemplary embodiment of theoptical sensor for determining dye concentrations in liquid media.

FIG. 1 shows an exemplary embodiment of an optical sensor 1 fordetermining dye concentrations in liquid media. In general, the opticalsensor can also be used for determining particle concentrations. Theoptical sensor can furthermore be used to determine dye or particleconcentrations in gaseous media. The optical sensor 1 is provided with ameasuring head, comprising a transmitting unit 2 and a receiving unit 3which are connected by means of supply lines 4, 4′ to an evaluation unit6 that is integrated into a housing 5.

The measuring head is connected by means of a connector 7 to theevaluation unit 6, wherein several and preferably identical measuringheads can in principle also be connected via separate connectors 7 tothe evaluation unit 6.

The transmitting unit 2 is provided with a semiconductor transmittingelement 9 which emits transmitting light rays 8. The receiving unit 3comprises a semiconductor receiving element 10 for receiving thetransmitted light rays 8. The semiconductor transmitting element 9 emitsvisible light rays 8 at a wavelength range of 400-700 nm, wherein thespectral bandwidth for the transmitted light rays 8 is smaller than 100nm. The semiconductor transmitting element 9 herein can be alight-emitting diode or a laser diode. For the present case, thesemiconductor transmitting element 9 is a GaN (gallium-nitride)light-emitting diode with a maximum radiation output at a wavelength of470 nm.

The semiconductor receiving element 10 consists of a phototransistor, aphotodiode, or a photo-resistor. The spectral sensitivity of thesemiconductor receiving element 10 is adapted to the wavelength of thetransmitting light rays 8. The photosensitive layer of the semiconductorreceiving element 10 preferably consists of cadmium selenide, cadmiumsulphide or mixtures thereof.

The transmitting unit 2 and the receiving unit 3 for the present caseare respectively provided with a light-permeable and liquid-impermeableencapsulation 11, 12 for accommodating the semiconductor transmittingelement 9 and/or the semiconductor receiving element 10. Theencapsulation 11, 12 consists, for example, of epoxy resins orpolymethacrylates. In principle, the encapsulations 11, 12 can alsoconsist of glass, Teflon, or polyolefins.

To form a beam with the transmitting light rays 8, a transmitting opticor a slit-shaped aperture can in principle be provided in thetransmitting unit 2. I addition, a monochromatic illuminator can beinstalled downstream of the semiconductor transmitting element 9 togenerate the monochromatic transmitting light rays 8.

An absorption measurement is realized with the optical sensor 1 todetermine the dye concentration in a liquid medium. The liquid medium inthat case is positioned inside an absorption section through which thetransmitting light rays 8 pass. The non-absorbed portion of thetransmitting light rays 8 impinges on the semiconductor receivingelement 10, thereby generating receiving signals at its output which arethen evaluated in the evaluation unit 6.

In principle, the absorption section can be a cell with transparentwalls, in particular a flow-through cell. In that case, the transmittingunit 2 and the receiving unit 3 are attached to the outside walls of thecell.

The measuring head for the present embodiment is designed as immersionsensor module which can be immersed into a rinsing basin or the like, soas to directly detect the dye concentration of the liquid mediumtherein. The optical sensor designed in this way in particular can alsobe used for determining particle concentrations in engine oils and/or inthe exhaust gases of motor vehicles.

For this, the transmitting unit 2 and the receiving unit 3 are securedon a holder 13 in such a way that a measuring gap with predeterminedwidth is created between these two units, thereby defining theabsorption section. The positions of the transmitting unit and thereceiving unit 3 on the holder 13 are preferably adjustable.

The evaluation unit 6 is used to trigger the semiconductor transmittingelement 9 and to evaluate the receiving signals present at the output ofthe semiconductor receiving element 10. A power pack 14 is provided inthe evaluation unit 6 for supplying power to the optical sensor 1. Thesemiconductor transmitting element 9 and the semiconductor receivingelement 10 are respectively supplied with a stabilized constant directvoltage. For this, a voltage stabilizer 15, 16 and a protective resistor17, 18 are respectively provided for activating the semiconductortransmitting element 9 and/or the semiconductor receiving element 10. Toavoid temperature drifting of the receiving signals, a thermistorcomponent such as a NTC resistor can additionally be integrated into thecircuit for the semiconductor receiving element 10. A thermistorcomponent of this type can also be used to compensate temperaturedrifting of the transmitting signals from the semiconductor transmittingelement 9. As an alternative or in addition, a suitable software modulecan also be provided in the evaluation unit 6 for compensating thetemperature drifting of the aforementioned components.

The evaluation unit 6 furthermore comprises an analog/digital converter19 as well as a downstream-connected computer unit 20. The analogreceiving signals are digitized in the analog/digital converter 19 andare then read into the computer unit 20 where the dye concentration ofthe liquid medium is determined by means of the receiving signals whichare read in.

The evaluation unit 6 can additionally be provided with an analog ordigital display unit, not shown herein, for displaying the actualreceiving signals.

The receiving signals, which can be either current signals or voltagesignals, are evaluated on the basis of the Lambert-Beer Law.

The optical sensor 1 is calibrated prior to the start of the operatingphase for the optical sensor 1. This calibration operation is realizedby means of reference measurements during which a liquid medium with aknown, predetermined dye concentration for the dye to be determined isrespectively arranged in the absorption section.

In the present case, two reference measurements are made during thecalibration operation. For the first reference measurement, theabsorption section contains a liquid medium without dye. The receivingsignals I_(o) determined during this first reference measurement arestored in the evaluation unit 6. For the second reference measurement,the liquid medium contains a predetermined dye concentration C_(cal) ofthe dye to be determined, wherein the dye concentration typically is inthe range of 0.5-1 g/l. The receiving signals I determined during thissecond reference measurement are also stored in the evaluation unit 6.

From these two measuring variables, a sensor-specific and dye-specificreference extinction value E_(cal) is then computed in the evaluationunit 6 based on the following equation:E _(cal)=1 g(I _(o) /I)=ε′dC _(cal)The above equation shows that the reference extinction value E_(cal) isdefined by the product of a fictional molar extinction coefficient ε′,the layer thickness d for the absorption section, meaning the width ofthe measuring gap between transmitting unit 2 and receiving unit 3, aswell as the predetermined dye concentration C_(cal) of the secondreference measurement.

The fictional molar extinction coefficient ε′ is defined by the productε′=ε·f,wherein ε is the molar, wavelength-dependent extinction coefficient andf is a correction factor which depends on the structure of the opticalsensor 1.

In the operating phase which follows the calibration, the dyeconcentration of the dye for which the calibration is carried out isdetermined for the liquid medium to be tested by conducting furtherabsorption measurements with the optical sensor.

The resulting receiving signals I_(meas) which form the actual measuringvalues are applied to the first reference measurement, in accordancewith the following equation:E _(meas) =Ig(I _(o) /I _(meas))=KC _(x)As a result, the extinction value E_(meas) is obtained as actualmeasuring variable which forms a measure for the dye concentration C_(x)to be determined.

The proportionality factor K is defined by the following equation:K=ε′·d

Following the conversion of the equations for E_(cal) and E_(meas), thedye concentration C_(x) is determined on the basis of the followingrelation: $\begin{matrix}{C_{x} = {\left( {E_{meas}/E_{cal}} \right)C_{cal}}} \\{= {\left\lbrack {\left( {{1{gI}_{0}} - {1{gI}_{meas}}} \right)/\left( {{1{gI}_{0}} - {1{gI}}} \right)} \right\rbrack C_{cal}}}\end{matrix}$This equation shows that the dye concentration C_(x) to be determined isdefined by the measuring values I_(o), I and I_(meas) as well as thepredetermined reference dye concentration C_(cal). The determination ofthe dye concentration therefore does not depend on the sensor-specificparameters, wherein it is particularly advantageous that nomonochromatic transmitting light is required for determining the dyeconcentration C_(x).

The following Table shows typical measuring results when using theoptical sensor 1 according to the invention for determining various dyeconcentrations in water as the liquid medium. TABLE 1 Dye concentrationconcentration Receiving computed from Devia- in the batch signalmeasuring signal tion Dye [g/l] [V] [g/l] [g/l] Water 0 2.380 0 0Remazol Deep 0.1 1.850 0.093 0.007 Black N 0.25 1.254 0.237 0.013 0.50.568 0.50 0.000 1.0 0.138*) 1.00 0.000 Remazol 0.1 2.308 0.120 0.020Brilliant 0.25 2.226 0.267 0.017 Blue R 0.5 2.101*) 0.500 0.000 1.01.880 0.947 0.053 Remazol 0.1 2.100 0.106 0.006 Brilliant Red 0.25 1.7640.254 0.004 F3B 0.5 1.398 0.470 0.030 1.0 0.731*) 1.00 0.000 Remazol 0.12.000 0.120 0.020 Yellow GR 0.25 1.600 0.307 0.057 0.5 1.213 0.520 0.0201.0 0.657*) 1.000 0.000

The above table shows that different dye concentrations were determinedfor four different dyes. The respectively predetermined dyeconcentration is entered in the left column of the table. For acomparison, the dye concentrations respectively computed from thereceiving signals present in the form of voltage signals are entered.The reference dye concentrations specified for the second referencemeasurements are respectively marked with *) in the table.

The table furthermore shows that a precise determination of dyeconcentrations in the liquid medium is given for a broad range ofconcentrations and a plurality of different dyes. It is particularlyadvantageous in this case if all measurements can be carried out withthe same optical sensor 1 which emits light rays 8 at a wavelength rangeof 470 nm. Selecting this transmitting wavelength range has provenadvantageous since a large number of dyes are highly light-absorbent inthis wavelength range.

Depending on the width of the measuring gap in the optical sensor 1, dyeconcentrations of up to 1 g/l or more can be determined.

The optical sensor 1 furthermore has the considerable advantage ofpermitting on location and under real-time conditions a determination ofthe dye concentrations of the respective liquid medium contained in oneor several basins by using one or several measuring heads. An opticalsensor 1 provided with several measuring heads can simultaneouslydetermine the dye concentration of liquid media at several measuringlocations, wherein the measuring signals are evaluated in the evaluationunit 6. The optical sensor 1 thus offers a particularly flexible andcost-effective option for determining the dye concentrations.

If the measuring head is designed as immersion sensor module, it can beused to¹ the dye concentration of the respective liquid media onlocation, in the basin, and nearly without delay. The optical sensor 1can therefore be used particularly advantageously for controlling andregulating waste-water control operations. In particular, the opticalsensor 1 can be used advantageously for the control of rinsing processesduring the washing of dyed and imprinted textiles.¹Note: This sentence is incomplete

REFERENCE NUMBER LIST

-   (1) optical sensor-   (2) transmitting unit-   (3) receiving unit-   (4,4′) supply lines-   (5) housing-   (6) evaluation unit-   (7) connector-   (8) transmitting light rays-   (9) semiconductor transmitting element-   (10) semiconductor receiving element-   (11) encapsulation-   (12) encapsulation-   (13) holder-   (14) power pack-   (15) voltage stabilizer-   (16) voltage stabilizer-   (17) protective resistor-   (18) protective resistor-   (19) analog/digital converter-   (20) computer unit

1. An optical sensor for determining the concentration of dyes and/orparticles in liquid or gaseous media, comprising at least one measuringhead with a transmitting unit (2), provided with at least onesemiconductor transmitting element (9) which emits visible light rays(8), as well as a receiving unit (3) provided with at least onesemiconductor receiving element (10) onto which the portion oftransmitted light rays (8) is guided which penetrates an absorptionsection filled with a liquid or gaseous medium, further comprising anevaluation unit (6) which is connected via electrical supply lines (4,4′) to the measuring head and is used for evaluating the receivingsignals presents at the output of the semiconductor receiving element(10) for determining the dye concentration and/or the particleconcentration.
 2. The optical sensor according to claim 1, characterizedin that it comprises several measuring heads which are connected to ajoint evaluation unit (6).
 3. The optical sensor according to claim 1,characterized in that the measuring head, or each measuring head, isembodied as immersion sensor module having a transmitting unit (2) and areceiving unit (3) which are encapsulated so as to be impermeable toliquid.
 4. The optical sensor according to claim 3, characterized inthat the transmitting unit (2) and the receiving unit (3) areencapsulated with light-permeable materials, at least in the region ofthe optically active surfaces for the semiconductor transmitting element(9) and the semiconductor receiving element (10).
 5. The optical sensoraccording to claim 4, characterized in that the light-permeablematerials are epoxy resins or polymethacrylates, glass, Teflon, orpolyolefins.
 6. The optical sensor according to claim 3, characterizedin that the transmitting unit (2) and the receiving unit (3) areattached to a joint holder (13) for defining the absorption section. 7.The optical sensor according to claim 6, characterized in that thetransmitting unit (2) and the receiving unit (3) can be securedadjustably in different positions on the holder (13).
 8. The opticalsensor according to claim 1, characterized in that a cell filled with aliquid or gaseous medium is provided to form the absorption section,wherein the transmitting unit (2) and the receiving unit (3) arearranged on the external surfaces of this cell.
 9. The optical sensoraccording to claim 8, characterized in that the cell is a flow-throughcell.
 10. The optical sensor according to claim 1, characterized in thatthe semiconductor transmitting element (9) is a light-emitting diode ora laser diode.
 11. The optical sensor according to claim 10,characterized in that the semiconductor transmitting element (9) emitstransmitting light rays (8) in the wavelength range of 400 nm to 700 nm.12. The optical sensor according to claim 11, characterized in that thespectral bandwidth for the semiconductor transmitting element (9) isless than 100 nm.
 13. The optical sensor according to claim 11,characterized in that the semiconductor transmitting element (9) emitslight rays (8) at the wavelength range of 470 nm.
 14. The optical sensoraccording to claim 10, characterized in that a monochromaticilluminator, a filter, a gap-type aperture, or a transmitting optic areinstalled downstream of the semiconductor transmitting element (9), inthe beam path for the transmitted light rays (8).
 15. The optical sensoraccording to claim 10, characterized in that the semiconductortransmitting element (9) is supplied with a constant direct voltage. 16.The optical sensor according to claim 1, characterized in that thesemiconductor receiving element (10) is a phototransistor, a photodiode,or a photo-resistor.
 17. The optical sensor according to claim 16,characterized in that the semiconductor receiving element (10) issupplied with a constant direct voltage.
 18. The optical sensoraccording to claim 17, characterized in that respectively one voltagestabilizer (15, 16) and one protective resistor (17, 18) are providedfor stabilizing the direct voltage supplied to the semiconductortransmitting element (9) and the semiconductor receiving element (10).19. The optical sensor according to claim 17, characterized in that athermistor component is additionally connected to the semiconductortransmitting element (9) for the temperature compensation of thetransmitting signals and/or to the semiconductor receiving element (10)for the temperature compensation of the receiving signals.
 20. Theoptical sensor according to claim 17, characterized in that a softwaremodule is provided in the evaluation unit (6) for the temperaturecompensation of the receiving signals.
 21. The optical sensor accordingto claim 1, characterized in that the evaluation unit (6) is providedwith an analog or digital display unit for displaying the receivingsignals.
 22. The optical sensor according to claim 1, characterized inthat the evaluation unit (6) is provided with a computer unit (20) forreading in the receiving signals via an analog/digital converter (19).23. A method for operating an optical sensor according to claim 1,characterized by the following methods steps: realizing referencemeasurements with known dye concentrations or particle concentrationsduring a calibration operation, using reference media arranged in theabsorption section, for determining a sensor-specific and dye-specificand/or particle-specific reference extinction value E_(cal);subsequently determining extinction values E_(meas) that form actualmeasuring variables for liquid or gaseous media arranged in theabsorption section; and, following this, determining the dyeconcentration or particle concentration in the respective liquid orgaseous medium by relating the measured extinction value E_(meas) to thereference extinction value E_(cal).
 24. The method according to claim23, characterized in that the reference extinction value is formedaccording to the equation E_(cal) =1 g(I_(o)/I_(cal)), wherein I_(o) andI_(cal) represent the signals received at the semiconductor receivingelement (10) for a dye-free and/or particle-free reference mediumarranged in the absorption section and a reference medium with apredetermined dye concentration and/or particle concentration C_(cal) ofthe dye and/or particles to be determined.
 25. The method according toclaim 24, characterized in that the extinction value E_(meas) whichforms the actual measuring variable is formed on the basis of theequation E_(meas)=1 g(I_(o)/I^(meas)), wherein I_(meas) is the signalreceived at the semiconductor receiving element (10) with the liquid orgaseous medium arranged in the absorption section for the dyeconcentration C_(x) of the dye and/or the particles to be determined.26. The method according to claim 25, characterized in that the equationC_(x)=(E_(meas)/E_(cal)) C_(cal) is used to determine the dyeconcentration and/or the particle concentration C_(x).
 27. The use ofthe optical sensor according to claim 1 for determining the soot contentand/or the metal abrasion content in engine oils.
 28. The use of theoptical sensor according to claim 1 for determining pollutants inexhaust gases of motor vehicles.
 29. The use of the optical sensoraccording to claim 1 for determining the particle concentrations inexhaust air.
 30. The use of the optical sensor according to claim 1 fordetermining pollutants in waste water.